1. Field of the Invention
The invention relates generally to electrical switching apparatus and, more particularly, to conductor connection assemblies for electrical switching apparatus such as, for example, circuit breakers. The invention also relates to methods for providing electrically insulated conductor connection assemblies.
2. Background Information
Electrical switching apparatus, such as circuit breakers, provide protection for electrical systems from electrical fault conditions such as, for example, current overloads, short circuits, abnormal level voltage conditions and other fault conditions. Typically, circuit breakers include an operating mechanism having a switching device structured to open electrical contact assemblies in order to interrupt the flow of current through the conductors of an electrical system in response to such fault conditions.
For example, circuit breakers, such as power circuit breakers for systems operating above about 1,000 volts, typically employ vacuum interrupters as the switching devices. Vacuum interrupters include separable electrical contacts disposed within an insulating housing. Generally, one of the contacts is fixed relative to both the housing and to an external electrical conductor, which is electrically interconnected with a power circuit associated with the circuit breaker. In the case of a vacuum circuit interrupter, the other contact is typically part of a movable contact assembly. The movable contact assembly usually comprises a stem of circular cross-section having, at one end, the contact enclosed within a vacuum chamber and, at the other end, a driving mechanism which is external to the vacuum chamber. Power circuit breakers and vacuum interrupters therefor, are discussed in further detail, for example, in U.S. Pat. No. 6,373,358, which is incorporated herein by reference.
Electrically energized or “live” components of electrical switching apparatus must be sufficiently electrically insulated from nearby components that are electrically conductive, in order to resist undesirable electrical shorts. For example, this is particularly true in view of the market trend to design power circuit breakers to be as small and compact as possible. Specifically, the joints where electrical connections are made between components of the circuit breaker, such as between each terminal (e.g., line terminal; load terminal) and the corresponding electrical conductor (e.g., line conductor; load conductor) of the circuit breaker are one area where it is particularly difficult to achieve the requisite level of electrical insulation.
One prior proposal for providing the desired electrical insulation has been to fully encapsulate the joint in an epoxy insulation. Specifically, the joint, including the fastener(s) (e.g., without limitation, screw; bolt) that secures the joint together, have traditionally been completely covered with the epoxy insulation coating, which is molded to the joint under relatively high temperature and/or pressure, or via insulating sleeves. As the epoxy cools, it hardens, thereby forming a tight, electrically insulative bond. However, such an encapsulating approach disadvantageously makes it difficult, if not impossible, to unfasten (e.g., separate or disconnect) the individual components of the joint once it has been assembled and encapsulated. It is desirable, therefore, to provide electrically insulated conductor connection assemblies that can be relatively easily unfastened (e.g., disassembled).
There is, therefore, room for improvement in conductor connection assemblies for electrical switching apparatus, such as circuit breakers, and in methods of providing electrically insulated conductor connection assemblies.